The present invention relates generally to a medium access control protocol for networks, and more particularly to a group randomly addressed polling method for wireless networks.
Personal communication services and next generation cellular communication are going to the direction of providing multiple cell network structure, even micro-cells or pico-cells. However, since the spectrum is so valuable that how to efficiently use it and provide seamless services is one of the most important issues in personal wireless communication. Among so many personal communication services, one of the hardest tasks is the wireless local data communication. With the emerging and developing of two technical trends, i.e. the lightweight portable high performance computers and critical demand of information exchange via data networks, the wireless local area network (wireless LAN) attracts great attention in the computer and communication industries. Under the great market demand, IEEE Computer Society has formed a standard studying group IEEE 802.11 Wireless LANs to standardize the high-speed wireless local area networks. The goal of the IEEE 802.11 is to define the physical transmission specification and medium access control scheme while other standards such as the logic link control keep unchanged. After couples of years' study, appropriate medium access control (MAC) for wireless LANs still remains open to the research community.
The requirements for the MAC protocol of wireless LANs are rather severe in the IEEE 802.11. Some of the important considerations are listed as follows for reference.
Throughput: Since the spectrum is a scare resource, the MAC protocol should utilize the spectrum very efficiently and achieve a high throughput. PA1 Multiple PHYs (physical layer transmissions): There should be only one MAC to serve multiple physical layer transmission methods which may be the direct-sequence spread spectrum (SS-DS), (slow) frequency-hopped spread spectrum (SS-SFH), diffused infrared, or narrow-band digital signal transmission, though they might have quite different transmission characteristics. PA1 Seamless Service: In the multiple-cell network environments which are different from the wireless voice networks, the data packets (or frames) must be received correctly and can not be dropped even during a handoff. PA1 Multi-cast: According to the study of traffic in the wireless LANs, it is discovered that the down-link, i.e. from the network to the mobile nodes, traffic dominates the whole traffic in the networks. If the wireless LANs with infrastructure are taken into consideration, such a down-link traffic is likely achieved through the base stations or repeaters which broadcast the data packets to the mobile nodes. The MAC protocol must support the multi-cast function. PA1 Synchronous Services: The MAC should have reasonable delay statistics to support the synchronous (time-bounded) services other than the data file transmission. PA1 Fairness: All users or mobile nodes should have equal opportunity to access the wireless LAN. The mobile nodes should be able to fairly register in the wireless LAN if they are qualified. PA1 Power Consumption: Since the mobile nodes are likely to be operated by a battery power, any MAC protocol to keep the mobile nodes listening to the base station(s) all the time should be avoided in the practical applications. PA1 Simple to Implement: In practical applications of the LAN environments, not only the mobile nodes but also the base stations should be able to be simply implemented. Traditional MAC (or multiple access) protocols for the wireless cellular-type networks use complicated hand-shaking procedures to complete a handoff. Within a cell which is known as the coverage of a base station, many protocols based on the token passing, carrier sensing, ALOHA have been proposed. They are, however, all facing some difficulties to be a perfect solution for the wireless LANs. At the same time, a more general MAC protocol should take both of the multiple access and handoff into consideration. Efforts have been made to develop a reasonable protocol in these years, but there is still no solution which can meet all of the MAC requirements for the wireless LANs now. The CDMA (Code Division Multiple Access) or B-CDMA (Broad-band CDMA) is hard to achieve the high-rate overlay data transmission in practical application due to the limitation of available spectrum and desirably simple base stations for the LAN applications. Therefore, how to develop a reasonable and appropriate MAC protocol for the wireless LANs is still a very important issue in this field. PA1 (a) when a respective base station is ready to conduct the up-link communication, the base station broadcasting a ready message to all users under its coverage; PA1 (b) each user generating at least one random number whenever becoming active; PA1 (c) all active users under the coverage of the base station simultaneously transmitting their random numbers to the base station in response to the ready message; PA1 (d) the base station collecting the random numbers, and polling the active users according to the collected random numbers; PA1 (e) when the base station successfully receives the packet of a respective active user, the base station sending a positive acknowledgment to the active user; and PA1 (f) when the base station unsuccessfully receives the packet of a respective active user, the base station sending a negative acknowledgment to the active user. PA1 (g) when there is a packet intending to be sent to one of the users in the down-link communication of the network, retrieving the representing address stored in the PBS location of the one user; PA1 (h) sending the packet to one of the base stations corresponding to the retrieved representing address; and PA1 (i) the one base station broadcasting and sending the packet to the one user.